imx: vf610 add get_cpu_rev

Since we need to support runtime check for different drivers, we need
to add get_cpu_rev for vf610, otherwise there will be build errors.

This patch introduces a dummy CPU id which is not read from chip
silicon. Later when we can get the real id from chip, can fix the
value of MXC_CPU_VF610 then.

Signed-off-by: Peng Fan <Peng.Fan@freescale.com>
Suggested-by: Stefano Babic <sbabic@denx.de>
Cc: Stefano Babic <sbabic@denx.de>
Acked-by: Stefano Babic <sbabic@denx.de>
diff --git a/arch/arm/include/asm/arch-imx/cpu.h b/arch/arm/include/asm/arch-imx/cpu.h
index be13b96..1c8d24e 100644
--- a/arch/arm/include/asm/arch-imx/cpu.h
+++ b/arch/arm/include/asm/arch-imx/cpu.h
@@ -21,6 +21,7 @@
 #define MXC_CPU_MX6D		0x67
 #define MXC_CPU_MX6DP		0x68
 #define MXC_CPU_MX6QP		0x69
+#define MXC_CPU_VF610		0xF6 /* dummy ID */
 
 #define CS0_128					0
 #define CS0_64M_CS1_64M				1